A wireless mesh network (WMN) is formed by multiple, possibly even hundreds or thousands or even more of radio nodes 101 that may communicate with each other, depending on e.g. transmission range, frequency channel usage, etc. The wireless mesh network 100 may have one or more sink nodes 102 that may be part of gateways to other networks 103, e.g. Internet. A simple example wireless mesh network 100 is illustrated in FIG. 1. Wireless mesh network may not be in static radio environment and part of the nodes may move, appear or disappear. Therefore, the example mesh network illustrated in FIG. 1 is self-organizing, and every node may do decisions independently, but supporting the network and its data delivery functionality.
One example of the wireless mesh network may be a wireless sensor network (WSN) formed by sensor devices that produce data. Each sensor device may be equipped with one or more radios that are used to deliver the data towards the sink node. Even if a single sensor radio cannot directly reach the sink node, the wireless mesh network formed between the sensor radio nodes takes care of it. A routing protocol implemented in each radio node chooses the way to the sink. Similarly, there may be data that is delivered, over multiple radio hops, from the sink to the node(s) or in between nodes.
The data transmitted in a WMN may have tight timing requirements, i.e. low latency communication requirements from node to node or node to sink delivery. As an example, in lighting system the switching control data should be delivered over the wireless mesh network quickly, e.g. within few hundreds of milli-seconds to create better user experience.
The data delivery should be fast, but on the other hand should not cause jamming to the network. Broadcasting/flooding may be the fastest way to deliver data to multiple receivers, but it also may cause collisions and increase interference. In case of larger networks, a non-controlled burst of broadcast messages may fully block the channels and impact the delivery of other data.
In broadcast communication, the tradeoff between reliability and communication overhead can be controlled with different amount of repetitions of the broadcast messages. In typical broadcast/flooding communication protocols, the amount of repetitions is node-specific and is typically the same for every node. This means, that in dense installations, the total amount of repetitions can be excessive and cause a large overhead resulting in e.g. large amount of collisions and interference. On the other hand, in sparse installation, the amount of repetitions may be too low to achieve sufficient reliability. Both of the outcomes may result in reduced quality of service, e.g. lost data and/or increased delays.
The target of this invention is to provide a method for maximizing reliability whilst minimizing overhead in broadcast communications.